In suspension photo with out wheels you can see 2x4 steel blocking below the frame and then 2x6 blocking below that.....then there is 2x6 cross framing front and back with intermediate cross framing as well..... That was 10" of blocking down ..... It only needed to he 7"

In the other photos you can see the bottom 2x6 is fine and there is now a 2x3 there.